This invention relates to collapsible fasteners, sometimes called one-piece blind fasteners, of a kind which serve as a nut plate. These fasteners have a head to bear against the exposed face of a structural member (workpiece) having a hole. These fasteners also have an expandable shank portion which bears against the blind (inaccessible) face of the structural member. The expandable shank or body has at least two slots to enable the fastener to split into pedals upon setting and some means of controlling the location where the pedals fold.
Buck U.S. Pat. No. 2,148,977 relates to a blind fastener of the general type collapsible fasteners but not apparently to those for use in heavy duty applications and not to be used as nut plates. The shank of the hollow plug in this prior art device is provided with slots cut clear through and with clear through holes cut in the center of the slots to control the location of folding. This technique may be suitable for light-weight blind fasteners but would be difficult and expensive to use with heavy duty fasteners.
Black et al. U.S. Pat. No. 3,667,340 is directed to what appears to be a heavy duty blind fastener. The fastener is fabricated by a series of extrusion steps. After the bore is punched out of the shank, a mandrel is inserted in the bore so that knives can cut slots in the shank without crushing it. Finally, a notching tool is inserted within the bore to cut a circumferential groove on the interior of the bore to control the location of folding. Black U.S. Pat. No. 4,416,572 teaches the same means of controlling the location of the fold.
Shackelford U.S. Pat. No. 3,789,728 teaches a heavy duty blind fastener in which multiple diameter bores are used to control the location of fold.
It is an advantage according to this invention to provide a fastener and a method of making it that does not require more than one machining step aside from tapping of threads. It is a further object to provide a novel means of controlling the location of the fold in the pedals upon setting.